Problem: Andrei wants to fill a glass tank with spherical marbles and then fill the remaining space with water. The variable $w$ models the amount of water (in liters) Andrei uses if he uses $n$ marbles. $w=32-0.05n$ What is the volume of each marble?
Explanation: The rate of change of the function is $-0.05$, which means every marble Andrei uses decreases the amount of water he uses by $0.05$ liters. This means each marble takes up $0.05$ liters in volume. The volume of each marble is $0.05$ liters.